This application claims a priority from German Application 100 50 542.2, filing date Oct. 11, 2000, and the contents of that application are incorporated by reference herein.
Use of automatic assembling machines for automatically placing, or mounting, electrical elements on circuit boards and the like is well known. Movement of an assembling arm is carried out via a pneumatic drive; that is, by a cylinder controlled by routing valves. These routing valves can be 3/2 routing valves or 5/2 routing valves, with two 3/2 routing valves completely filling or exhausting air of the associated cylinder, while a 5/2 routing valve can only switch the direction. A pressurized air supply to a plurality of cylinders via the routing valves is provided via at least one main air valve.
Particularly during installation work on the assembling machines, including also repair work, work must be carried out with pressurized cylinders in a system.
German Patent Document DE 196 13 848 C2 discloses a safety circuit to control a hydraulic drive in which at least one safety circuit overlies a regulating circuit in such a manner that if the regulating circuit cuts off a driven part can only be controlled by the respective safety circuit. This safety circuit carries out a defined opening or closing. The hydraulically overlaid safety circuit assures that a hydraulic switch function is set in a defined manner, independently of the condition of the remainder of the system of the hydraulic circuit and its control elements, with the otherwise normal control operation via the regulating circuit being deactivated in a defined manner. The circuit condition of the control block and, therefore, the exciting condition of magnets are ignored.
Such a safety circuit cannot be used for an installation operation, because, in this regard, work must often be carried out in a system having pressurized cylinders. Further, a safety circuit having this structure for assembling machines is too expensive.
So that during adjustment work of assembling machines, with protection doors being open and with safety functions being intentionally bridged, no inadvertent activation of the cylinder takes place, a mandated level of safety must be created for installation personnel in accordance with European Community machine regulations. An inadvertent activation is particularly possible if there are errors in the control. In this regard, dangerous movements of the pressurized cylinders could take place.
Publication of German Patent Document DE 100 01 735 A1 discloses a protection apparatus for protecting against an inadvertent activation of operation of a machine assembly that has the purpose of assuring secure protection during installation and maintenance, as well as during repair work, in dangerous areas of machine apparatus. With the help of at least one decentralized control-panel element, a stationary control signal is created in dependence on a protection requirement and delivered to a central power switch, which is then opened.
Thus, it is an object of this invention to provide a safety circuit, as well as a method to control such a safety circuit, for an installation, or mounting, operation of an assembling machine that allows one to work thereon, even with pressurized drives with a disarmed, or bridged, protector.
According to principles of this invention, a safety circuit for protecting against an inadvertent activation of a pneumatic drive of an automatic assembling machine, of a type having at least one vertical cylinder and one horizontal cylinder, with each being controlled by a multi-way valve and fed by a primary pneumatic circuit, further includes two pneumatic control circuits that automatically switch into and out of the primary pneumatic circuit, such that the vertical cylinder and the horizontal cylinder, after the switching into, does one of remaining in its current position and moving to a rest position.
In a process of this invention, for the control of a safety circuit to protect against an inadvertent activation of a pneumatic drive of an automatic assembling machine, an opened and closed switching of a pneumatic primary circuit is caused by two pneumatic control circuits, respectively, according to an activated mode of operation set by a system control (SPS) of the automatic assembling machine, with the two safety control circuits not being activated during normal operation with an existing protection and a closed protective door, but the safety control circuits being activated in any one of the following circumstances:
during normal operation without a protection being present;
upon the protective door (Sxc3x9c) being opened and there being a closed protective bridging;
upon an EMERGENCY-OFF with an open contact (PNOZ) of an EMERGENCY-OFF protection on the automatic assembling machine, and
during installation without protection and with protection bridging as well as another closed contact (EB).
It is provided that a safety circuit comprising two pneumatic control circuits are included in an assembling machine that are switched into and out of a pneumatic primary circuit of drives, that is of cylinders, of the assembling machine, depending on the type of operation. The safety circuit should have particular influence on the system during installation operations and should also automatically counter errors in the control, so that, for controlling, in addition to the SPS (Memory Programmable Control), all parts cooperating with the SPS, such as valves or relay circuits for example, play important roles.
The additional pneumatic control circuits have at least one control-path valve, with two openable check valves for each cylinder.
Control of the check valves takes place via the control-path valve in each control circuit that is controlled by a hardware-structured electronic logic, with additional contactors being used on existing switches, or protectors.
This logic is adapted to the respective type of operation, so that various safety functions can be realized depending on the type of operation. In addition a further protection can be included in the safety circuits to monitor the electrical voltage supply and an additional pressure monitor, which is a pneumatic-electrical converter, for recognizing a failure (disappearance) of a pressurized-air supply.
An additional software-type monitoring of the pneumatic function in the pneumatic circuits takes place through pressure monitors that deliver signals that are evaluated by the SPS. Thus, high resistance to errors is achieved, meeting DIN EN 954-1.
Further enhancements of the invention are described.
For example, a uniform color marking of one or both of the additional pneumatic control circuits by use of colored hoses is provided. In this manner, the functions can be more easily arranged, with, for example, the red hoses being for closing the line, that is locking the pressure in, and the blue hoses for exhausting. Also, retrofit changes, for example adding a drive to the system by changing the hoses on the control ports of the check valves, are possible, with which, among other things, various dangers can be reacted to, even on site upon placing a machine in operation.
This safety circuit realizes in an uncomplicated manner a pressure-free switching of most drives as well as pressurized-air trapping of all relevant drives upon a danger-preventative safety measure xe2x80x9cMACHINE-STOPxe2x80x9d without protection bridging (for example upon xe2x80x9cEMERGENCY OUTxe2x80x9d or xe2x80x9cOPEN PROTECTIVE DOORxe2x80x9d).
By pressurized-air trapping upon the safety measure MACHINE-STOP, a protection against the falling of a load, for example, or a sudden stopping of quick movements can be achieved.
During operation with protection bridging, all drives are closed, so that an inadvertent switching of the path-valves in the primary pneumatic circuit, for example because of control errors, does not result in dangerous movements of drives.